A hydraulic fluid powered driven member commonly includes a driven member and a hydraulic motor. The driven member may be a sprocket, a sweeper brush, a screw, a gear, a winch, a cutter, a horizontal or vertical drilling or boring assembly, or any other device. When the driven member is a winch, the winch commonly includes a spool upon which a cable is wound and a motor to provide power to the spool. The spool is connected to the motor, generally through a gear train. Operation of the motor results in rotation of the spool for, depending upon the direction of rotation, extending or retracting an amount of cable from the spool.
Hydraulic motors powered by hydraulic fluid from a fluid pressure source, and electric motors powered by electricity from an electrical power source, are both commonly used to power spools. Applications for motor driven spools include winches as mentioned above, in which the winch cable is wrapped around the spool multiple times. Other applications for motor powered spools may include conveyor belts and drive belts, in which an endless conveyor belt or drive belt wraps partially around the spool and is driven by the spool to convey goods or to drive other devices. Hydraulic motors may offer an advantage over electric motors to drive spools, and particularly spools that are used in winches, by offering a higher power density (power per unit of volume) than electric motors.
U.S. Pat. No. 6,095,500 discloses the use of low speed high torque hydraulic motors for powering a hydraulic winch spool. According to the disclosure of that patent, the motors are either gear reduction motors, which may use a complicated series of gears to lower the speed and achieve higher torque for the spool, or radial piston motors, which may require a complicated fluid system for providing fluid to the various pistons and their associated cylinders.
It is also known to directly drive the spool of a winch with a hydraulic motor. U.S. Pat. No. 7,261,277 discloses a hydraulic motor that is located adjacent an end of a winch spool and that is operable to rotate the spool when a clutch is engaged.
U.S. Pat. No. 4,457,677 discloses a low speed high torque hydraulic motor in which an outer ring of the assembly is fixed to and rotates with a drive shaft. An inner star is held against rotation by a universal shaft assembly.
Additionally, high efficiency, high flow, two speed hydraulic gerotor motors are known that use two separate power elements on a common rotating output shaft. An integral selector valve shifts between a parallel fluid connection among the power elements to provide high torque low speed operation and a series fluid connection among the power elements to provide low speed high torque operation. In the high torque low speed parallel operation mode, the motor provides twice the torque and half the speed relative to the low torque high speed series operation mode. The selector valve can be open center or closed center and may be actuated by an external pilot or optional solenoid valve. This type of hydraulic motor is available from Parker Hannifin Corporation, Hydraulic Pump and Motor Division, as a series 700 hydraulic motor and is further described at www.parker.com.
Increasing the line pull (force applied to the cable by the winch) and the length of the line while decreasing the overall dimensions and weight of the winch may be desirable for any winch. Also, decreasing the complexity and cost of the winch may be desirable. This may be particularly true with non-stationary winches, including those carried on vehicles where space may be limited and added weight may negatively affect vehicle performance.